THE COMMON BRAKES. 235 
surface of the frond, while the other membrane lies over the spore- 
cases as if it were simply a recurved margin. The former we are 
inclined to regard as a true indusium, while the latter is probably 
of the nature of an accessory indusium, such as occurs in the 
Dicksonieœ, only there the fructification is broken up into short or 
punctiform sori. We have elsewhere pointed out* that this structure 
appears to be the same as that which occurs in the long doubtful 
genus Pœsia; the plant on which the latter genus was founded being, 
we believe, the Pteris scalaris of recent authors, in which short sub- 
rotund sori occasioned by the breaking up of the margin into smaller 
lobes, occur in company with others of the more usual elongated 
pteroid form. The name Pesia consequently has the priority, if it 
is ultimately found necessary to remove these plants from the other 
species of Pteris; in which case the genus would constitute a 
8 Pœsœœ of the Polypodiacee in the neighbourhood of the Lindsœœ. 
The Bracken is the most abundant of our wild Ferns, occurring 
in woods, thickets, heaths, and waste places, apparently avoiding a 
chalky soil: this latter cireumstance however, according to Mr. C. 
Johnston, being rather due to the ordinary shallowness of the soil 
over that rock, than to any prejudicial influence in the chalk itself. 
It is spread over Great Britain, from Cornwall to Shetland, the 
Orkneys, and the Hebridean Islands of North Uist, Harris, and 
Lewis; and is plentiful also in Ireland and the Channel Isles, 
descending to the coast-level, and reaching an elevation of nearly 
2000 feet in the Highlands of Scotland. "When growing exposed, 
it is a harsh rigid-looking plant, but when in its most luxuriant 
state, in sheltered lanes or woods, it is extremely beautiful, its expan- 
sive fronds, eight to ten feet or more in height, gracefully arching 
out from among the brushwood. 
This is a common Fern through Europe, as it appears to be also 
in most other parts of the world, many so called exotie species being 
without sufficient distinguishing characters. Its northern limit in 
Europe appears to be in Lapland, in about 67^ N., where, according 
to Wahlenberg, it is rare. In Asia, it is found in the Caucasus; in 
* Moore, in Gardeners’ Chronicle, 1858, 878. 
ZZ [u 

